GF07.10-P-1041MMI Engine Timing, Start/Stop Function

GF07.10-P-1041MMI Engine Timing, Start/Stop Function
ENGINES 152.9 in MODEL 172.4

The ECO start/stop function is subdivided into the engine-side and the on-board network side scope
The partial function "engine timing, start/stop function" is viewed in terms of the engine timing system.
Information for partial function "Energy management start/stop function" is documented in the function description "Energy management function".

Function requirements for the engine timing start stop function, general points
^ Engine running
^ Outside temperature in the range: -10°C greater than T less than 40°C
^ System diagnosis complete and fault-free
^ Speed of 8 km/h exceeded once during forward travel

Engine timing, start/stop function, general points
For a stationary vehicle, the ECO start/stop function switches the engine off automatically and starts it again, as soon as the driver wishes to drive off. The fuel consumption and thus the exhaust emissions are reduced by stopping the engine with the vehicle at a standstill.
Conventional cutout and starting of the engine with the transmitter key (A8/1) or via the KEYLESS-GO start/stop button (S2/3) (for code (889) Keyless Go) continues to be possible.

The ME-SFI [ME] control unit (N3/10) permanently performs an SD and assesses the system conditions for the ECO start/stop function.

All systems participating on the ECO start/stop function permanently check their status and transmit this via the chassis CAN (CAN E) to the ME-SFI [ME] control unit

If the function requirements are fulfilled, the driver is notified of ECO start/stop function readiness by the "ECO" symbol in the multifunction display (A1p13) in the instrument cluster (A1).

Engine timing, start/stop function, function sequence
The ECO Start-stop function consists of the following partial functions:

^ Function sequence for engine stop
^ Function sequence for engine start
^ Function sequence for forced engine start

Function sequence for engine stop
The engine is switched off by the ME-SFI [ME] control unit if all of the following function conditions are fulfilled:

- Indicator lamp for the ECO start/stop function button (N72/1s50) lights up (system is fault-free and the ECO start-stop function is activated)
- Vehicle speed = 0 km/h
- Coolant temperature greater than 60°C and less than 115°C
- Transmission oil temperature greater than 10°C and less than 120°C
- Engine oil temperature in the specified value range
- Engine rpm in specified value range
- Transmission oil temperature greater than 10°C and less than 120°C
- Gear range "D" or "N"
- Accelerator not operated
- Service brake actuated up to standstill of the vehicle
- Adequate vacuum (-1050 mbar up to 90 mbar) in brake booster
- Engine hood closed
- No crash signal
- Steering wheel angular velocity in the specified value range
- Condition of the on-board electrical system OK
- Driver door closed
- Driver seat belt applied
- Interior temperature regulated

For the start-stop function the ME-SFI [ME] control unit reads in the following sensors and signals:

- Coolant temperature sensor (B11/4)
- Accelerator pedal sensor (B37), accelerator pedal actuation
- Crankshaft Hall sensor (B70), engine speed
- Instrument cluster, vehicle speed via chassis CAN
- Supplemental Restraint System control unit (N2/10), direct crash signal
- Supplemental restraint system control unit via chassis CAN:
- Indirect crash signal
- Status of driver seat belt
- Front SAM control unit with fuse and relay module (N10/1) via the chassis CAN:
- Engine stop prohibition
- Engine start request
- Signal that engine hood is closed
- ECO start/stop function button (N72/1s50) status
- Automatic air conditioning control and operating unit (N22/7) via the body CAN and chassis CAN:
- Air conditioning status
- Engine stop prohibition
- Engine start request
- Electronic Stability Program control unit (N30/4) via the chassis CAN:
- Brake actuation
- Wheel speed
- Engine start request
- Engine stop enable
- Engine stop prohibition
- Radar sensors control unit (N62/1) for code (233) DISTRONIC PLUS, for code (237) Active Blind Spot Assist, engine torque request (increasing or reducing) via the chassis CAN
- Steering column module control unit (N80) via the chassis CAN:
- Steering wheel angle
- Steering wheel angular velocity

- Fuel system control unit (N118), fuel pressure via the drive train CAN (CAN C)
- Fully integrated transmission control control unit (Y3/8n4), status of drive stage via drive CAN

Upon opening of the engine hood in automatic engine stop the ECO start-stop function is switched off and all indicator lamps in the IC light up. The engine must be restarted using the transmitter key or over the start/stop button KEYLESS-GO (for code (889) Keyless Go).

Function sequence for engine start
The engine is started automatically for actuation of the accelerator pedal.
The ME-SFI [ME] control unit actuates the circuit 50 starter relay (N10/1kM) with a ground signal. The power contact on the relay closes and the starter solenoid switch (M1) is supplied at "circuit 50" with a voltage from "circuit 30".
The FSCU receives the CAN signal "fuel specified pressure" from the ME-SFI [ME] control unit via the drive train CAN and appropriately actuates the fuel pump (M3) by means of a pulse width modulated signal (PWM signal).

Function sequence for a forced engine start
The forced engine start subfunction is available as a protection function. Here the engine is force started autonomously (without any action taken by the driver) by the ME-SFI [ME] control unit if one of the following function conditions occurs:

- On-board network condition requires the engine to run
- Coolant temperature greater than 115°C
- Exceeding of the engine stop period of a maximum of 3 minutes
- A/C required engine running (e.B. windshield fogged up)
- Vacuum on brake booster not in the nominal range (-1050 mbar up to 90 mbar)
- Driver presence recognition (driver seat belt or driver door is opened)
- Change of the steering wheel angle by more than 8°
- Vehicle speed greater than 2 km/h for forward travel and immediately for recognition of rolling backwards
- System or communication error of the following systems: driver presence, steering, on-board electrical system, brake and control systems, accelerator pedal, transmission, starter, engine

A maneuvering process is recognized for an engaged gear range "R" and the ECO start/stop function is deactivated. If the engine is stopped it is force started by the system and the engine stop function is suppressed if it is running.
The ECO start/stop function is subsequently activated again for an engaged gear range "D" and for exceeding a vehicle speed of 15 km/h.
The engine is also started if the driver door is opened, the seat belt buckle for the driver opened or the ECO start-stop function over the ECO button is switched off.